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The DESGW program is a collaboration between members of the Dark Energy Survey, the wider astronomical community, and the LIGO-Virgo Collaboration to search for optical counterparts of gravitational wave events, such as those expected from binary neutron star mergers or neutron star-black hole mergers. While binary black hole (BBH) events are not expected to produce an electromagnetic (EM) signature, emission is certainly not impossible. The DESGW program has performed follow-up observations of four BBH events detected by LIGO in order to search for any possible EM counterpart. Failure to find such counterparts is still relevant in that it produces limits on optical emission from such events. This is a review of follow-up results from O1 BBH events and a discussion of the status of ongoing uniform re-analysis of all BBH events that DESGW has followed up to date.

Summary

Abstract

This work is intended to provide an introduction to multiwavelength observations of low-mass X-ray binaries and the techniques used to analyze and interpret their data. The focus primarily is on ultraviolet, optical, and infrared observations and their connections to other wavelengths. The topics covered include outbursts of soft X-ray transients, accretion disk spectral energy distributions, orbital light curves in luminous and quiescent states, superorbital and suborbital variability, line spectra, system parameter determinations, and echo mapping and other rapid correlated variability.

4.1 Introduction

The first X-ray binary to be observed and identified as such was Scorpius X-1 (Giacconi et al., 1962), although several other systems were known as optical stars or novae before this. Within a few years, optical and radio counterparts to Sco X-1 were discovered (Sandage et al., 1966; Andrew and Purton, 1968), and the topic has remained multiwavelength in nature since then.

This work is intended to provide an introduction to some of the observational characteristics of X-ray binaries suitable for a graduate student or an advanced undergraduate. My aim was to produce a primer for someone relatively new to the field rather than a comprehensive review. Where appropriate, I also discuss techniques for analysis and interpretation of the data. The focus is almost exclusively on low-mass X-ray binaries, in which the accretion disk is most accessible to multiwavelength observations, and is predominantly biased toward ultraviolet, optical, and infrared observations and their relation to observations at other wavelengths. For a textbook treatment of accretion astrophysics in general, the reader is referred to Frank et al. (2002) and for more comprehensive reviews of X-ray binaries to Lewin et al. (1995) and Lewin and van der Klis (2006).

Correlations between the radio and X-ray bands in the hard state of black hole X-ray binaries (BHBs) have led to the discovery of the Fundamental Plane of black hole accretion, linking accretion-driven radiative attributes to black hole mass. Although this discovery has led to new constraints on radiative efficiencies, there is still significant degeneracy in terms of understanding the governing physics. I present several new results exploring the processes driving the Fundamental Plane over the black hole mass range. These include the first ever homogeneous fits of sources at approximately the same Eddington luminosity but millions of times different in mass, which I focus on for this proceeding article.

CuInS2 films are often grown in a two-step process with the deposition of a Cu-In alloy followed by high temperature sulphurisation in either S vapour or H2 S. Numerous techniques exist for the deposition of Cu-In. In this work Cu-In films have been deposited on tin oxide coated glass using the electroless deposition technique, a low cost, low temperature approach. The films were found to consist of a two layered structure. Initially, Cu islands grew forming a layer on the substrate. The deposition process subsequently produced dendritic Cu-In alloys from the tops of the Cu islands. Various CuIn phases were observed, namely Cu9In4 and CuIn, the presence of which was related to the solution pH. None of the films were found to contain metallic In, indicating that this process may be well suited to subsequent high temperature sulphurisation.

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